The rotor assembly of a compressor typically comprises an impeller mounted to a shaft that is driven by a motor. Imbalance in the rotor assembly places increased loading on the bearings used to mount the rotor assembly within the compressor, thereby reducing the lifespan of the bearings. The rotor assembly is therefore ideally balanced prior to mounting within the compressor. However, it is not always possible to balance the rotor assembly as a complete unit prior to mounting within the compressor. Instead, it is often necessary to assemble the various components of the rotor assembly within the compressor. Accordingly, while the individual components may be balanced, the completed rotor assembly may not be. Moreover, even when it proves possible to dynamically balance the rotor assembly, imbalance often subsequently arises as a result of component wear and thermal distortion.